seg fault on emitWakeUpSignal call in the result_callback lamda function

[saravan-kumar]

I have a TreeExecutor and on execution of a simple behavior tree with just a sequence and multiple action clients as children.
The cancellation of the tree results in a seg fault on emitWakeUpSignal call in the result_callback lamda function of bt_action_node action client (observed using gdb backtrace).

[saravan-kumar]

Writing a clear description on the issue and how to reproduce it in this comment.

Issue

I have BT executor, and I start executing a tree with a just a sequence and ROS action client in this sequence. I cancel this goal, and the result request for cancel times out and when i start executing the tree again, the delayed result is now being processed and the result tries to wake up a already exited tree, resulting in a seq fault

To Reproduce

Steps to reproduce the issue using btcpp_ros2_samples pkg

1. Add this sleep in line 68 to reproduce a delay in the result from the server

+ rclcpp::sleep_for(std::chrono::seconds(3));

BehaviorTree.ROS2/btcpp_ros2_samples/src/sleep_server.cpp

Lines 67 to 73 in 7a6ace6

	if(goal_handle->is_canceling())
	{
	result->done = false;
	goal_handle->canceled(result);
	RCLCPP_INFO(this->get_logger(), "Goal canceled");
	return;
	}

2. Use this behaviour tree :

<root BTCPP_format="4">
  <BehaviorTree ID="SleepActionSample2">
    <Sequence>
      <SaySomething message="start"/>
      <SleepAction name="sleepA" action_name="sleep_service" msec="20000"/>
      <SaySomething message="sleep completed"/>
    </Sequence>
  </BehaviorTree>
</root>

3. Build the package
4. Run the sample_bt_executor that launches both the bt_executor and sleep server with

ros2 launch btcpp_ros2_samples sample_bt_executor.launch.xml

5. Start executing the tree:

ros2 action send_goal /behavior_server btcpp_ros2_interfaces/action/ExecuteTree "{target_tree: SleepActionSample2}"

6. Cancel the goal using:

ros2 service call /behavior_server/_action/cancel_goal action_msgs/srv/CancelGoal

7. Now do Step 5 again and it shoud crash

ENVIRONMENT:

• ROS Version humble
• BT.ROS2 branch - humble

Error Details from GDB Bt

Thread 35 "sample_bt_execu" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fffd37ee640 (LWP 1081281)]
0x00007ffff7be7608 in BT::TreeNode::emitWakeUpSignal() () from /home/saravana/do
cker22.04/ddiplus_ws/install/behaviortree_cpp/lib/libbehaviortree_cpp.so
(gdb) bt
#0  0x00007ffff7be7608 in BT::TreeNode::emitWakeUpSignal() ()
   from /ws/install/behaviortree_cpp/lib/libbe
haviortree_cpp.so
#1  0x00007ffff03bd6f1 in BT::RosActionNode<btcpp_ros2_interfaces::action::Sleep
>::tick()::{lambda(rclcpp_action::ClientGoalHandle<btcpp_ros2_interfaces::action
::Sleep>::WrappedResult const&)#3}::operator()(rclcpp_action::ClientGoalHandle<b
tcpp_ros2_interfaces::action::Sleep>::WrappedResult const&) const ()
   from /ws/install/btcpp_ros2_samples/share/b
tcpp_ros2_samples/bt_plugins/libsleep_plugin.so
#2  0x00007ffff03c9077 in void std::__invoke_impl<void, BT::RosActionNode<btcpp_
ros2_interfaces::action::Sleep>::tick()::{lambda(rclcpp_action::ClientGoalHandle
<btcpp_ros2_interfaces::action::Sleep>::WrappedResult const&)#3}&, rclcpp_action
::ClientGoalHandle<btcpp_ros2_interfaces::action::Sleep>::WrappedResult const&>(
std::__invoke_other, BT::RosActionNode<btcpp_ros2_interfaces::action::Sleep>::ti
ck()::{lambda(rclcpp_action::ClientGoalHandle<btcpp_ros2_interfaces::action::Sle
ep>::WrappedResult const&)#3}&, rclcpp_action::ClientGoalHandle<btcpp_ros2_inter
faces::action::Sleep>::WrappedResult const&) ()